"Diver's" Law

The name of the discoverer is not known to the ChemTeam. It may even be that this law has never been "discovered" in the manner we speak of the discovery of Boyle's Law. Diver is not a name, it refers to diving beneath the water. The deeper you go the greater the pressure because of the larger amount of water pressing down on you.

This law gives the relationship between pressure and amount when the temperature and volume are held constant. Remember amount is measured in moles. Also, since volume is one of the constants, that means the container holding the gas is rigid and cannot change in volume.

If the amount of gas in a container is increased, the pressure increases.

If the amount of gas in a container is decreased, the pressure decreases.

Why?

Suppose the amount is increased. This means there are more gas molecules and this will increase the number of impacts on the container walls. This means the gas pressure inside the container will increase. It will stay at this higher level because the container walls do not move (the volume is constant).

The mathematical form of Diver's Law is: P ÷ n = k

This is a direct mathematical relationship.

Let P1 and n1 be a volume-amount pair of data at the start of an experiment. If the amount is changed to a new value called n2, then the pressure will change to P2.

We know this: P1 ÷ n1 = k

And we know this: P2 ÷ n2 = k

Since k = k, we can conclude that P1 ÷ n1 = P2 ÷ n2.

This equation of P1 ÷ n1 = P2 ÷ n2 will be very helpful in solving Diver's Law problems.

Click this sentence for a video using Diver's Law. Instead of moles, the problem uses the word particles. The problem works wih either the word 'particles' or 'moles.' That's because, to convert from particles to moles, you divide both 'particle's-values' by the same, constant value, that value being Avogadro's Number.